This invention relates to motorcycle transmissions and, more particularly, to a five speed motorcycle transmission with coaxial input and output drive means at one end of a common driveshaft means.
While five speed motorcycle transmissions have been heretofore developed, and are commercially available on motorcycles of some manufacturers, such as the Triumph Motorcycle Corporation, as far as I am aware, all prior five speed motorcycle transmissions have included only a direct drive and four lower gear ratio drives. In addition, the provision of conventional five speed motorcycle transmissions having axially spaced input and output drive means requires particular consideration of space limitations and arrangement of parts. Certain transmission arrangements, such as in motorcycles manufactured by the Harley-Davidson Motor Company, have not heretofore included a five speed transmission because of lack of available space and lack of a solution to more compact arrangement of parts.
The present invention provides a compact five speed transmission including a high speed overdrive gear arrangement, a high speed direct drive gear arrangement, and three low speed gear arrangements. In addition, conventional four speed transmissions, such as the four speed motorcycle transmission manufactured by the Harley-Davidson Motor Company for "Electra Glide-1200" and "Super Glide-1200" Harley-Davidson motorcycles, can be easily replaced by the present transmission.
In general, a conventional Harley-Davidson four speed transmission includes a gear housing which is approximately 73/4 inches long, 7 inches wide, and 5 inches deep. A main drive shaft is rotatably mounted in the housing in parallel spaced relationship to a non-rotatable countershaft fixedly mounted in the housing. A first group of four gears are mounted on the rotatable main drive shaft in engagement with a second group of four gears mounted on the countershaft. Two drive dogs are utilized to transmit input torque through various gear combinations and to the output providing the four gear speed ratios.
In general, the present invention involves the following major changes and modifications to the conventional four speed Harley-Davidson transmission:
1. Lengthening the gear housing by 5/8 inches. PA1 2. Adding bearing mounts and bearings to the housing for rotatably mounting the countershaft. PA1 3. Replacing the countershaft and driveshaft with shafts that are 5/8 inches longer. PA1 4. Providing different gear arrangements and mountings which include adding an overdrive gear cluster, separating all of the countershaft mounted gears, and decreasing the overall width of the gears by 5/8 inches. PA1 5. Adding an extra drive dog for the overdrive gear cluster. PA1 6. Eliminating the speedometer drive gear. PA1 1. Providing a longer shifter shaft with an additional shifter fork. PA1 2. Providing a longer cam plate with an extra cam track. PA1 3. Increasing the number of teeth on the shifter gear. PA1 4. Increasing the size of the shifter casting.
In addition, the conventional shifter mechanism utilized on Harley-Davidson four speed transmissions can be easily replaced to accomodate the five speed transmission of the present invention. The Harley-Davidson shifter generally comprises: a single shifter shaft mounted above and between the driveshaft and countershaft for mounting axially displaceable shifter forks which are used to position the drive dogs for engaging various combinations of gears; a tumbler-like cam plate shifter having grooved cam tracks for guiding cam followers on the shifter forks for positioning the shifter forks; and a rachet type shifter gear for rotating the cam plate.
In general, this conventional Harley-Davidson shifter mechanism can be replaced to accomodate the transmission of the present invention by making the following changes and modifications:
More specifically, the transmission of the present invention comprises: gear housing means for enclosing transmission system components; driveshaft means rotatably mounted in the housing; countershaft means rotatably mounted in the housing parallel to and radially spaced from the driveshaft; input drive means operably connected to one end of the driveshaft means for transferring input torque from the motor to the driveshaft means; output drive means freely rotatably mounted on the driveshaft means for transferring torque from the transmission to an output such as the rear wheel of a motorcycle; torque shifting and transmitting means rotatably locked to but axially displaceable on the driveshaft means and on the countershaft means for selectively transmitting torque between transmission components; a first group of gears mounted on the driveshaft means in continuous engagement with a second group of gears mounted on the countershaft means, with the gears arranged and mounted such that the torque shifting and transmitting means can selectively engage various combinations of gears to transmit torque from the driveshaft means to the countershaft means to the output drive means, in four different gear ratios and directly from the driveshaft means to the output drive means in a one to one gear ratio.